A mouse polyomavirus (MPV) virus-like particle (VLP) is a hollow nanoparticle formed by self-assembly of major coat protein VP1 (42 kDa) and has great potential in vaccinology, gene therapy, drug delivery, and materials science. MPV VLP consists of 72 capsomers (Caps) positioned at a T=7d lattice inclining to the right, each of which comprises five VP1 molecules.
VP1, purified after expression in prokaryotic cells, can exist as Cap and self-assembles into VLP which is homogeneous in formation and stable in structure under proper in-vitro conditions. This in-vitro VLP production method has a broad application prospect for reasons of simplicity and efficiency. To date, a yield of up to 4.38 g L−1 of VP1 with an N-terminal GST tag has been achieved from a pH-stat fed-batch high-cell-density process. While the GST tag could enhance the soluble expression of VP1 protein and improve the ease of tagged precursor purification, the subsequent enzymatic removal of the GST tag with expensive thrombin followed by additional separation and purification of the removed GST tag from the reaction system leads to complex operation and high cost, which present a daunting challenge in the expansion of production, thus limiting the applications of MPV VLP.
Affinity chromatography capable of separating and purifying a target molecule by interaction between biomacromolecules and specificity ligands is advantaged by high selectivity, high efficiency, mild operating condition, etc. The ligand is crucial for affinity chromatography as the realization of affinity chromatography depends on the specificity identification between the target molecule and the ligand. Peptide ligands have a significant development prospect for their high affinity, high stability, little proneness to degradation, simple production, and the like. With the rapid development of molecular simulations in recent years, designed screening has been achieved for high-specificity affinity peptide ligands by simulating target protein-ligand interactions that have already existed in natural world, and thus the screening efficiency and accuracy of the affinity peptide ligands are improved.
A MPV Cap and minor coat protein VP2 (35 kDa) complex is a naturally-existing Cap-ligand complex. The C-terminus of VP2 (thereafter termed VP2-C) binds in an unusual, hairpin-like manner into the inner surface of Cap through hydrophobic interactions. Herein a design basis of affinity peptide ligands of Caps has been developed.